Table of contents:
Video: Peltier Elements Or Free Electricity From A Fire
2023 Author: Douglas Hoggarth | [email protected]. Last modified: 2023-05-24 11:23
- Thermoelectric module design
- We collect TEM for 5 V
- Energy furnace
Any chemical process takes place with the release of various kinds of energy. Such a powerful source as combustion has been used at all times. It can be called the primary source of heat and light. Almost all substances on Earth burn, while emitting heat and light in different quantities. Converting thermal energy into electrical energy is not difficult if you have a working steam turbine at hand, similar to those installed at the CHP. This is a bulky and complex device, which is unlikely to find a place in the boiler room of a country house. We will try to benefit from the heat generated by stove heating or heating water.
The Peltier effect is the phenomenon of temperature difference when thermocouples of two different types of conductors (p-type and n-type) interact when a direct current passes through them. The Seebeck effect is a consequence of the Peltier effect, when an electric current is generated when one of the thermocouples is heated. We will not describe the thermodynamics of the process in detail - this information, which is difficult to understand, can be easily found in the reference literature. We are interested in the result and options for its practical use.
Thermoelectric module design
Thermoelectric module (TEM) consists of many thermocouples connected by a copper plate. The thermocouple field is glued between two ceramic plates. It is possible to assemble such a module only in the factory. But it will be possible to assemble several TEMs for your own needs at home. Peltier-Seebeck elements are readily available in specialized stores (and websites) selling technological equipment.
We collect TEM for 5 V
What you need:
- Peltier module TEC1-12705 (40x40) - 2 pcs.;
- step-up converter of constant voltage EK-1674;
- duralumin sheet 3 mm thick;
- a water tank with a perfectly flat bottom (bucket);
- hot glue;
- soldering iron.
We cut out two identical plates from a sheet of duralumin, a little more than two modules lying side by side. We fix the plates on the modules on both sides with hot melt glue. We fix (hot glue) the resulting "sandwich" to the bottom of the bucket. Such a design can already be put on fire, but we will get useless 1.5 V at the output. To improve the characteristics, we need a step-up converter, which we solder into the circuit. It will raise the voltage to 5V, which is enough to charge a mobile phone.
Attention! The converter has dimensions of 1.5x1.5 cm. In the absence of professional skills, entrust the soldering to a specialist.
The temperature difference in our design is obtained by heating one side (from a furnace or flame) and cooling the other (water in a ladle). Of course, the larger the difference, the more efficient the module will work. Therefore, to operate in the microgenerator mode, a relatively low water temperature in the ladle is required (it is better to replace it periodically). To generate the coveted 5 V, it is enough to put the structure on a glass with a burning candle.
By proportionally combining more modules, we get a more efficient power generation system. Accordingly, by increasing the structure, we proportionally increase the heat exchanger. In this case, the surface to be cooled must be completely covered with a container of water (the simplest and most affordable option).
Everything is so simple that immediately there is a desire to assemble more modules into one system and generate 220 V from the fire. And then plug in an oil heater or air conditioner. Such a simple system has its drawbacks, and the main one is low efficiency. Usually this figure does not exceed 5%. This leads to a relatively low current strength of 0.5 - 0.8 A and a very low power - up to 4 W.
For a pump or an incandescent lamp, this is negligible, but quite sufficient for:
- charging batteries up to motorcycle (in versions proportional to the requirements);
- work of light-emitting diode (LED) lamps;
- radio receiver.
In winter, the system, placed on a heat source located outside, will work as efficiently as possible.
The cost of materials for assembling a thermoelectric microgenerator for 5 V:
|Peltier module TEC1-12705 (40x40) * - 2 pcs.||600||Price for 2 pcs.|
|DC voltage boost converter EK-1674||320|
|Duralumin||300||Sheet for bucket version|
|Hot melt glue Radial||150||2 ml|
|Total for materials||1470|
* - this item model was selected for price reasons. The range of TEMs from supplier companies is quite wide, which allows you to choose more efficient (up to 8 V) models (they are significantly more expensive).
Factory products of this design are just beginning to appear on sale. Serial production is carried out in small batches, and the range is small. The cost of such a "ladle" starts at 2500 rubles.
A factory thermogenerator is a device based on the Peltier-Seebeck effect, which can be fixed directly to a heated surface. From the design described above, it is distinguished by its factory design (which means reliability), the absence of a liquid heat exchanger (instead of it - fins for air cooling) and a higher price.
A standard "travel" thermogenerator has the following characteristics:
|Current strength||0.16 A|
|The weight||1.6-2 kg|
|Set of standard connectors||Yes|
|Dimensions (approx)||150x150x200 mm|
|Price||From 7000 rub.|
As you can see from the table, factory reliability and utility are not cheap. At the same time, it cannot be said that it is functionally superior to the home-made version with a bucket. An impressive 13.5 volts will speed up cell phone charging, but you will need to carry 2 kg of weight with you on the hike, which is an unaffordable luxury (given the size of the device). And, of course, the price makes you think. For this amount, you can collect not a "thermal bucket", but a "thermal pan" and calmly charge your laptop. And one more nuance - the device still requires fixing on a metal plate in case of using an open flame.
In general, this is a pleasant and convenient addition for those who have no problems with money and free space in the trunk.
To date, the energy furnace is the apotheosis of the use of TEM in everyday life. This is a factory product, in fact a stove-stove, for any type of solid fuel with an integrated thermoelectric module. Ideal for hunting lodges, summer cottages, remote wintering grounds and, in general, any kind of life away from civilization. Designed for autonomous use (without peripheral heat sinks), has only a hearth and chimney. Provides for cooking. The most powerful Peltier-Seebeck elements are installed on this furnace.
Energy furnace characteristics:
|output power||25-50 W|
|Output voltage||12 in|
|Firebox volume||30-60 liters|
|The weight||30-60 kg|
|Thermal power||4-6 kW|
Although the oven is portable, it is certainly the “heavyweight weight class” among household appliances. However, the range of tasks for an energy furnace is quite wide - it can even charge car batteries, illuminate entire rooms with LED lamps. She will find a place in the expedition wagon train and in the hunting all-terrain vehicle, in the technical room and in the country. In other words, in this case, we always have a heat source with us, it remains to find fuel.
In its niche, the energy furnace is irreplaceable, although the service life declared by the manufacturer - 10 years is a little alarming. It should be noted that, as in the thermogenerator, there is a possibility of preventive (or emergency) replacement of all parts up to the body.
Thermoelectric modules are extremely interesting objects. In addition to the applications described, they are also used for water and air conditioning. In this case, a direct current is supplied to the same element and it works "in the opposite direction" - it cools the air. This technology is successfully applied in automobile air conditioners and water coolers, in the automotive industry and in the manufacture of microprocessors. We will describe these devices in the next article.